Test system for multiple switchboards.



Patented Aug. 6, I90l. H. G. WEBSTER. TEST SYSTEM FOR MULTIPLESWITCHBOARDS.

(Application filed Oct. 29, 1900.)

(No Model.)

. 171-0612 for:

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m: NONRIS mus UNITED" STATES PATENT OFFICE.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE STROMBERG-CARLSON TELEPHONE MANUFACTURING COMPANY, OF SAME PLACE.

TEST SYSTEM FOR MULTIPLE SWITCHBOARDS.

SPECIFICATION forming part Of Letters Patent N0. 679,805, dated August6, 1901. Application filed October 29, 1900. Serial No. 34,771. (Nomodel.)

To all whom it may concern.-

Be it known that I, HARRY G. WEBSTER, a

' citizen of the United States, residing at Ohification.

My invention relates to a testing system for multiple switchboards, andits object is the provision of a system for giving an audible signal tothe operator when the line called for is in use by diversion of aportion of the current of the main battery without the use of anauxiliary testing-circuit and battery. By means of my invention formaking the test I am able to avoid complication of the circuits of theboard and at the same time provide a reliable and effective test.

In carrying out my invention I provide means for diverting a portion ofthe current of the main battery for the purpose of testing and at thesame time avoid the diversion of so large anamount of current that itwill interfere with the operation of the system.

In this system the plug-tips are when insorted in the jacks allconnected to one side of the battery, while the sleeves of the plugs areconnected through the instruments included in circuit with the otherside of the battery. When the answering-plug is inserted in the jack ofthe subscriber called and the listening-key is operated, the operatorstelephone is bridged across the line.

In my invention Iarrange a circuit in shunt of the bridge, including theoperators telephone, which is adapted to be closed by the answering-plugwhen a line called for is,en-.

gaged at another board, and I provide in this shunt test-circuitresistance sufficient to allow a fraction of the current to fiow enoughto give the indicating-signal in the operators telephone. 1

My invention I have illustrated in the accompanying drawing, and I willdescribe it in detail with reference to this drawing.

Two substationsA and B are each equipped with the telephonic appliancesand the signalbells usual in common battery systems and each connectedthrough line-wires a a b b, respectively, with spring-jacks c c d d upondifferent sections of the multiple switchboard at the exchange. Theansweringq'acks e (2' may be considered as appearing upon the sectionswith the spring jacks c d. The double plugs ff are shown with theircordcircuits and the instruments included therein.

In addition there is shown inserted in the spring-jack (1 one plug of apair at another section to illustrate the condition of the circuits whena line is in use.

I have illustrated diagrammatically the operators telephone g and thegenerator h with the respective listening and ringing keys g h allincluded in the cord-circuit. Connected also with one side of thecord-circuit is the clearing-out drop 70, which is also connected withthe positive side of the battery Z. Ihave shown also the clearing-outdrop with its connection to the cord-circuit of the second section. Theclearing-out indicator 7a, which may be assumed to be at the board wherethe plug sis located, is included in circuit with the subscriberstelephone-line, and the continuity of the circuit through theclearing-out drop is controlled by the gravity switch-hook at thesubscribers station, so that when the gravity switch-hook is relieved ofthe influence of the telephone-receiver the clearing-out indicator isplaced in one condition of use, and when restored to its normal positionby the receiver when it is replaced the clearing-out indicator is placedin another condition of use. I have not shown the complete cord-circuitof the second section, as this is unnecessary, the cord-circuits beingidentical at the different sections, and I have left out all unnecessarydetails, illustrating only, and that in a diagrammatic way, theessential features of my present invention.

Connected to the primary of the inductioncoil of the operators telephoneat a point between its extremities or to another coil inductivelyassociated with the secondary of the induction-coil is the circuit m,which is adapted to be connected to one side of the cord-circuit by theoperation of the operators listening-key. By this means there isconnected in the'shunt-circuit around the battery the coil n, which ispreferably a portion of the primary and is connected with the negativeside of the battery at 0 and completes its circuit through the contactpand the operators listening-key g, the tip of the plug f, the thimble qof the spring-jack d, the sleeve of the plugs, the clearing-out drop is,and the positive side of the battery, thus giving an audible signal tothe operator when the circuit Wanted is in use at another board.

The resistance of this test-circuit is low and so related to the branchincluding the operators telephone that a sufficient current will flowover the test-circuit to give the desired signal.

To indicate the method followed in the op eration of my system, I willdescribe the operation as it is practiced in an exchange embodying thissystem of testing.

When the subscriber at one of the stations, as A, lifts his telephonefrom the hook, the circuit is completed through the lines to the centraloffice through the battery I and through the subscribers drop 0", thusthrowing the annunciator and indicating to the operator the fact that asubscriber has called for a connection. The operator inserts one plug ofa pair in the answering-jack and with the tip of the other plug touchesthe thimble in front of the spring-jack of the subscriber called for, asd. This thimble is in a normally open circuit connected ,to similarthimbles associated with the spring-jacks of the same subscriber uponall the other boards. If the line is not in use, this test-circuitincluding the thimbles being open, no signal will be given to theoperator. The plug will then be inserted into the spring-jack and thesignal given to the subscriber called by means of the ringing-key h. If,however, as indicated in the drawing, the subscriber called for shall beconnected with another subscriber at a difierent board, the test-circuitincluding the thimbles will be connected with the sleeve of the plug andthrough the sleeve to the positive side of the battery. Then upontouching the tip of the plug to the thimble the circuit will becompleted from the positive side of the battery through the clearing-outdrop it, the thimbles, the tip of the plug f, and, the operatorslistening-key being depressed, the circuit m, including the coil 91, tothe negative side of the battery. The resistance in this circuit is lowenough so that some current will flow through coil n sufiicient to givea positive signal to the operator, showing that the line called for isbusy.

It will be seen that with my invention it is not necessary to use thelines running to the subscribers stations to complete thetestingcircuit, and no auxiliary battery or testingcircuit is required.It will be further apparent that I have provided a test system whereinthe operator while testing may at the same time listen to the callingsubscriber, this re sult being accomplished by reason of the fact thatthe entire primary of the operators transmitter is not included in alocal circuit, but a special primary-coil portion that is preferably apart of the operators complete primary coil that is employed for talkingpurposes, this special primary-coil portion being in inductive relationwith the secondary of the operators outfit.

While I have shown my system of testing as applied to the special formof multipleswitchboard system illustrated and described herein, it willbe apparent to those skilled in the art that modifications in the systemmay be made and my invention still be employed. I do not wish,therefore, to limit myself in my application to the precise system shownand described nor to the exact details set forth herein; but,

Having thus described an embodiment of my invention, what I claim asnew, and desire to secure by Letters Patent, is

1. In a multiple-switchboard telephone-exchange system, the combinationwith a plurality of telephone-lines extending from subscribers stationsto an exchange, each telephone-line being connected at the exchange withjacks upon a number of sections of a multiple switchboard,cord-connecting apparatus for uniting subscribers for conversationincluding a testing-plug, connected thimbles for the jacks of each line,the said test-plugs being provided with tip and sleeve portions, thesleeve portions being adapted for connection with the test-thimbles wheninserted, an operators telephone appliance, a listeningkey forconnecting same with and disconnecting it from the cord-circuit, a coilportion n in inductive relation with the second ary of the operatorstelephone appliance, a battery connected between one terminal of thesaid coil portion and the sleeve-strand, the remaining terminal of thecoil portion being adapted for connection with the tip of thetesting-plug upon the operation of the listening-key, and a second coilportion also in inductive relation with the secondary coil of theoperators telephone appliance adapted for inclusion in a subscriberstelephonic circuit, substantially as described.

2. In a multiple-switchboard telephone-ex change system, the combinationwith a plurality of telephone-lines extending from subscribers stationsto an exchange, each telephone-line being connected at the exchange withjacks upon a number of sections of a multiple switchboard,cord-connecting apparatus for uniting subscribers for conversationincluding a testing-plug, connected thimbles for the jacks of each line,the said test-plugs being provided with tip and sleeve portions, thesleeve portions being adapted for connection with the test-thimbles wheninserted, an operators telephone appliance, a listeningkey forconnecting same with and disconnecting it from the cord-circuit, a coilportion it in inductive relation with the secondary of the operatorstelephone appliance, a

battery connected between one terminal of the said coil portion and thesleeve-strand, the remaining terminal of the coil portion being adaptedfor connection with the tip of the testing-plug upon the operation ofthe listening-key, a second coil portion also in inductive relation withthe secondary coil of the operators telephone appliance adapted forinclusion in a subscribers telephonic circuit, and a clearing-outindicator included in circuit with the battery and the sleeve of thetesting-plug, substantially as described.

3. In a multiple-switchboard telephone-exchange system, the combinationwith a plurality of telephone-lines extending from subscribers stationsto an exchange, each telephone-line being connected at the exchange withjacks upon a number of sections of a multiple switchboard,cord-connecting apparatus for uniting subscribers for conversationincluding a testing-plug, connected thimbles for the jacks of each line,the said test-plugs being provided with tip and sleeve portions, thesleeve portions being adapted for connection with the test-thimbles wheninserted,an operators telephone appliance including inductively-relatedprimary and secondary coils, a listening-key for connecting the samewith and disconnecting it from the cord-circuit, a battery interposedbetween the primary winding and the sleeve of said plug, and a conductorconnected between the terminals of the primary winding and adapted forconnection with the tip of the test-plug upon the operation of thelistening-key,said

listening-key serving to include the operators telephone appliance incircuit with the sub scribers line, whereby a portion of the primarywinding may be included in the testcircuit while the entire primarywinding may be included in circuit with a subscribers line,substantially as described.

4. In a multiple-switchboard telephone-exchange system, the combinationWith a plurality of telephone-lines extending from subscribers stationsto an exchange, each telephone-line being connected at the exchange withjacks upon a number of sections of a multiple switchboard,cord-connecting apparatus for uniting subscribers for conversationincluding a testing-plug, connected thimbles for the jacks of each line,the said test-plugs being provided with tip and sleeve portions, thesleeve portions being adapted for connection with the test-thimbles wheninserted, an operators telephone appliance including inductively-relatedprimary and secondary coils, a listening-key for connecting the samewith and disconnecting it from the cord-circuit, a battery interposedbetween the primary winding and the sleeve of said plug, a conductorconnected between the terminals of the primary winding and adapted forcon neetion with the tip of the test-plug upon the operation of thelistening-key, said listeningkey serving to include the operatorstelephone appliance in circuit with the subscribers line, whereby aportion of the primary winding may be included in the test-circuit whilethe entire primary winding may be incl uded in circuit with asubscribers line, and a clearing-out indicator included in circuit withthe battery and the sleeve of the testingplug, substantially asdescribed.

In witness whereof I hereunto subscribe my name this 27th day ofOctober, A. D. 1900. HARRY G. WEBSTER.

Vfitnesses:

CHARLES A. BROWN, CHARLES E. HUBERD,

